1. Field of the Invention
The present invention relates to an image forming apparatus, an authentication method, and a recording medium having an authentication program embodied therein.
2. Description of the Related Art
Recent image forming apparatuses including printers can perform printing operations based on print requests received from plural personal computers (PCs) connected through a network such as a LAN. To specify PCs that can cause an image forming apparatus to perform printing operations, the print requests sent from the PCs often have attached user authentication information containing information about PC users.
When an image forming apparatus receives a print request and user authentication information from a PC, the image forming apparatus performs authentication based on the user authentication information. If authentication succeeds, the image forming apparatus performs a printing operation based on the print request. On the other hand, if authentication fails, the print request is cancelled, so that no printing operation is performed. In this way, it is possible to specify PCs that can cause an image forming apparatus to perform printing operations.
In company offices, for example, an external authentication server holds such user authentication information. If an image forming apparatus receives a print request and user authentication information, the image forming apparatus queries the external authentication server for authentication based on the received user authentication information. In response to the query, the external authentication server performs authentication and sends the authentication result to the image forming apparatus. The image forming apparatus controls image forming operations based on the received authentication result.
Various inventions have been devised to effectively perform such authentication operations.
Patent Document 1 discloses a technique of permitting use of plural services by a single entry of user authentication information. This technique is for holding user authentication information entered upon use of a service and thereby omitting an authentication operation upon use of another service.    <Patent Document 1> Japanese Patent Laid-Open Publication No. 2005-202923
According to the invention disclosed in Patent Document 1, every time authentication using user authentication information stored in a client device is needed for permitting use of a service, an authentication apparatus such as an external authentication server is requested to perform authentication. Thus, a large workload is placed on the external authentication server.
Take another example in which a user instructs a printer to print ten copies of a document from a PC with Windows OS (trademark) running an application Excel (trademark); since Excel (trademark) creates a separate job for each copy, the PC sends ten sets of a print request and user authentication information to the printer. The printer queries an external authentication server for authentication based on each of the received ten sets of user authentication information. This might lock up (overload) the external authentication server.